It would be hard to do based on demographics.
A
sign in West Virginia would sale for less then a shop in a city of California
So now you would be going for a state or country wide average.
This now would have you in the same place you are now.
Then there is the shop that will drive down the price to get the job.
This hurts him you and all other
sign companies in your area.
Once he is out of business because he did not make a profit but work all the time.
The businesses left standing are there to fix the damage he created by under bidding.
So I would suggest come to a price that makes you a profit instead of trading dollars for dollars.